Electric switchgear having integral earthing contacts



Oct. 4, 1966 s. BEDDOE ETAL ELECTRIC SWITCHGEAR HAVING INTEGRAL EARTHING CONTACTS 4 Sheets-Sheet 1 Filed Dec. 12, 1963 FIG.4

s. BEDDOE ETAL 3,277,252

ELECTRIC SWITGHGEAR HAVING INTEGRAL EARTHING CONTACTS Oct. 4, 1966 4 Sheets-Sheet 2 Filed Dec. 12, 1963 Oct. 4, 1966 s. BEDD OE ETAL 3,277,252

ELECTRIC SWITCHGEAR HAVING INTEGRAL EARTHING CONTACTS 4 Sheets-Sheet 5 Filed Dec. 12, 1963 Oct. 4, 1966 s. BEDDOE ETAL 3,

ELECTRIC SWITCHGEAR HAVING INTEGRAL EARTHING CONTACTS Filed Dec. 12. 1963 4 Sheets-Sheet 4 APPLICANTS SLWey Beddoe 8r. John Molyneux United States Patent 3 277,252 ELECTRIC swITcHGEAR HAVING INTEGRAL g I EARTHING CONTACTS Stanley Beddo'e and John Molyneux, Liverpool, England, assignors to The English Electric Company Limited, London, England, a British company Filed Dec. 12, 1963, Ser. No. 330,093 Claims priority, application Great Britain, Dec. 17, 1962,

. 7,49'3/ 62 v Claims. (Cl. 200-50) This invention relates to electric switchgear.

A known type of electric switchgear comprises a fixed part, a circuit-breaker assembly arranged to be movable axially relative to said fixed part between service and isolat'ed" positions, two pairs of co-operating main contacts, one contact of each pair being mounted on the circuit-breaker assembly and the other contact of each pair being mounted on said fixed part, circuit-breaker means in series with said main contacts mounted on the circuitbreaker. assembly, said main contacts mounted on the circuit-breaker assembly axially engaging those mounted on the fixed part in the service position of the circuitbreaker' assembly and being isolated therefrom in the isolated position thereof.

The main contacts mounted on the fixed part are connected respectively to the line and busbar.

It is an object of the present invention to provide earthing contacts, integral with the switchgear, by which one or both the main contacts mounted on the fixed part of the switchgear may be connected to earth through the circuit-breaker, when the circuit-breaker assembly is in the isolated position.

According to the invention, at least one pair of earthing contacts is associated with at least one pair of co-operating main contacts, one contact of said pair of earthing contacts being mounted on the circuit-breaker assembly, and the other contact of said pair of earthing contacts being mounted on said fixed part, one of said contacts of .said pair of earthing contacts being capable of being extended to engage the other contact of said pair of earthing contacts when the circuit-breaker assembly is in its isolated position, and means to earth the other main contact mounted on the circuit-breaker assembly, whereby a main contact mounted on said fixed part may be earthcd through said pair of earthing contacts and through the circuit-breaken Preferably a pair of such earthing contacts is associated with both said pairs of main contacts. Preferably also the earthing contacts are arranged coaxially within the associated main contacts.

One embodiment of switchgear in accordance with the invention will now be described with reference to the accompanying drawings, of which:

FIG. 1 shows the switchgear contacts in the serv position;

FIG. 2 shows the contacts in an earthed position;

FIG. 3 shows the contacts in the isolated position;

FIG. 4 shows .a side elevation of the switchgear with the contacts in the earthed position, and

FIG. 5 shows a detail of the upper half of FIG. 2.

Referring now to FIG. 4, the movable circuit-breaker assembly 1 6 is mounted on pairs of wheels 39, 40 running on rails 38 so as to be axially movable from the fixed part 10 0f the switchgear from the position shown in FIG. 1 to that shown in FIG. 2. To move the circuitbreaker assembly door 46 is opened and rod 4 4 which has a rotatable tommy bar 4 5- at its end is rotated transmitting rotation through a pin 43 to a threaded rod 41. A support 48 allows rod 41 to rotate freely within it but prevents end movement of rod 41. Rotation of rod 41 in an internally threaded support 42 fixed to the circuit-breaker assembly 16 results in movement of the circuit-breaker assembly.

In the position shown in FIG. 1, the fixed part 10 of the switchgear comprises upper and lower main contacts 1 1, 12 mounted in an insulating housing 13. One of the contacts 11, '12 is connected to an incoming cable and the other to a busba-r. The insulating housing 13 is formed with outwardly-projecting spouts 14, 1'5 surrounding the contacts.

The movable circuit-breaker assembly 1 6 comprises a block 17 of insulating material in which are fixed two main contacts, in the form of hollow copper tubes 18, 19, the spacing of which corresponds to the spacing of the fixed contacts 11, 12. The ends of the tubes 18, 19 carry cluster contacts 20, 21, which are dimensioned to engage the contacts 11, 12. The block 17 has projections which surround the tubes 18, 19, and fit within the spouts 14, 15.

A circuit-breaker 22 has its arm 23 pivotally mounted on the end of tube 19 remote from the cluster contacts 21, the movable contacts 24 mounted on the arm engaging fixed contacts 25 which are electrically connected to the end of tube 18 remote from cluster contact 20.

Short rods 26, 27 are mounted coaxially within, and in electrical contact with, the upper and lower fixed contacts 11, 12, and form earthing contacts. Sliding contacts 28, 29 are mounted to slide coaxially within the tubes 18, 19, with which they are in electrical contact, by means of bushes 30, 31 at the end of the tubes 18, 19, adjacent the cluster contacts. The sliding contacts are in the form of elongated rods and have small cluster contacts 32, 33, at their ends which are dimensioned to engage the rods 26, 27, and which, in the service position, shown in FIG. 1, lie coaxially within the main cluster contacts 20, 21.

The sliding contacts 28, 29 can be moved between the extended position shown in the upper half of FIG. 2, and the retracted position shown in the lower half of FIG. 2 by a key 49 externally threaded at one end to engage an internal thread in sliding contacts 28, 29 as shown in FIG.- 5, where the contact 28 is extended to engage the earthing contact 26, with the movable assembly 16 in the retracted or right-hand position as seen in the figure. Pivotally-mounted shutters 34, 35 are mounted on the fixed part 10 to be capable of swinging over the mouth of the respective spout 14, 15, to prevent access to thecontact housed in the Sp-out" which may, under certain circumstances, be energized, and the shutters 34, 315 are each formed with short rods 36, B7 of similar dimensions to the contacts 26, 27. The shutters 3 4, 35 are connect-ed to earth, for example through flexible braided wire.

In the service position shown in FIG. 1, current flows from the fixed contact 11 through cluster contact 20 and tube 18 to the circuit-breaker 22 and thence through tube 19 and cluster contact 21 to the fixed contact 12.

In the position shown in FIG. 2, the fixed contact 11 is connected to earth through the earthing contact 26, cluster contact 3 2, sliding contact 28, bush 30, tube 18, circuit-breaker 22, tube 19, bush .31, sliding contact 29, cluster contact 33, rod 37, and shutter 35, the fixed contact 12 being isolated. It will be evident that the fixed contact 12 may be connected to earth through the circuit-breaker 22 and shutter 34, with the contact 11 isolated, by reversing the position of the appropriate parts.

In the position shown in FIG. 3, the movable assembly 16 is in the retracted position, the sliding contacts 28, 29 are retracted within the tubes 18, 19, and the fixed contacts 11, 12 are thus isolated.

It will be noted that the cross-section area of the earthing contacts is less than that of the corresponding main contacts: eg, the cross-section area of the sliding contacts 2-8, 29 is considerably less than that of the tubes 18, 1 9; the cross-section area of the cluster contacts 32, 33 is considerably less than that of those 20, 21; and the cross-section area of the earthing contacts 26, 27 is considerably less than that of the main contacts 11, 12.

Moreover, the earthing contacts 26, 27 form an integral part of the fixed part of the switchgear, and the sliding contacts 2 8, 29 and the cluster contacts 32, 33 form an integral part of the movable circuit-breaker assembly 16.

What we claim .as our invention and desire to secure by Letters Patent is:

1. Electric switchgear comprising a fixed part, a circuit-breaker assembly arranged to be movable relative to said fixed part between service and isolated positions, two pairs of co-operating main contacts, one contact of each pair being mounted on the circuit-breaker assembly and the other contact of each pair being mounted on said fixed part, circuit breaker means in series with said main contacts mounted on the circuit-breaker assembly, said main contacts mounted on the circuit-breaker assembly axially engaging those mounted on the fixed part in the service position of the circuit-breaker assembly and being isolated therefrom in the isolated position thereof, at least one pair of earthing contacts associated with at least one pair of co operating main contacts, one contact of said pair of earthing contacts being mounted coaxially within and in electrical contact with one contact of the pair of main contacts, and the other contact of said pair of earthing contacts being mounted coaxially within and in electrical contact with said other contact of the pair of main contacts, one of said pair of earthing contacts being slidably mounted and so dimensioned as to be capable of being extended to engage the other contact of said pair of earthing contacts when the circuitbreaker assembly is in its isolated position, and earthing means including an earthed contact to earth the other main cont-act mounted on the circuit breaker assembly.

2. Electric switchgear comprising a fixed part, a circuit-breaker assembly arranged to be movable axially relative to said fixed part between service and isolated positions, first and second main contacts mounted on said fixed part, third and fourth main contacts mounted on said circuit-breaker assembly, said first main contact cooperating with said third main contact and said sec-nd main contact co-operating with said fourth main contact in the service position of the circuit-breaker assembly and being isolated therefrom in the isolated position thereof, circuit-breaker means in series with said third and fourth main contacts, at least one pair of earthing contacts associated with at least one pair of co-operating main contacts, one contact of said pair of earthing contacts being mounted coaxially within and in electrical contact with said third main contact, and the other contact of said pair of earthing contacts being mounted coaxially within and in electrical contact with said first main contact, one of said pair of earthing contacts being slidably mounted and so dimensioned as to be capable of being extended to engage the other contact of said pair of earthing contacts when the circuit-breaker assembly is in its isolated position, and earthing means including .an earthed contact to earth said fourth main contact mounted on the circuit-breaker assembly.

3. Electric switchgear as claimed in claim 2 wherein one contact of said pair of earthing contacts comprises a cluster contact. A

4. Electric switchgear as claimed in claim 2, wherein said earthed contact is mounted on an insulating, outwardly-projecting annular member and comprises, a pivotally-mounted shutter mounted to be capable of swinging over the mouth of said outwardly-projecting annular.

member.

5. Electric switchgear comprising a fixed part, a cirmounted on said circuit-breaker assembly, said first main 7 contact co-operating with said third main contact and said second main contact co-operating with said fourth main contact in the service position of the circuitbreaker assembly and being isolated therefrom in the isolated position thereof, circuit-breaker means in series with said third and fourth main contacts, first, second, third and fourth earthing contacts associated each with the corresponding main contact, said earthing contacts being mounted coaxially within and in electrical contact with the corresponding main contact, said third and fourth earthing contacts being slidably mounted and so dimensioned .as to be capable of being extended to engage respectively said first and second earthing contacts when the circuit-breaker assembly is in its isolated position, and comprising earthing means including an earthed contact selectively to earth said third and fourth main contacts, whereby said first and second main contacts may selectively be earthed through the first and third earthing contacts and the second and fourth earthing contacts respectively and through said circuit-breaker ROBERT K. SOHAEFER, Primary Examiner.

KATHLEEN H. CLAFFY, Examiner.

ROBERT S. MACON, M. GI NSBURG,

69 Assistant Examiners.

relative to said fixed part between service and iso-t 

5. ELECTRIC SWITCHGEAR COMPRISING A FIXED PART, A CIRCUIT-BREAKER ASSEMBLY ARRANGED TO BE MOVABLE AXIALLY RELATIVE TO SAID FIXED PART BETWEEN "SERVICE" AND "ISOLATED" POSITIONS, FIRST AND SECOND MAIN CONTACTS MOUNTED ON SAID FIXED PART, THIRD AND FOURTH MAIN CONTACTS MOUNTED ON SAID CIRCUIT-BREAKER ASSEMBLY, SAID FIRST MAIN CONTACT CO-OPERATING WITH SAID THIRD MAIN CONTACT AND SAID SECOND MAIN CONTACT CO-OPERATING WITH SAID FOURTH MAIN CONTACT IN THE "SERVICE" POSITION OF THE CIRCUITBREAKER ASSEMBLY AND BEING ISOLATED THEREFROM IN THE "ISOLATED" POSITION THEREOF, CIRCUIT-BREAKER MEANS IN SERIES WITH SAID THIRD AND FOURTH MAIN CONTACTS, FIRST, SECOND THIRD AND FOURTH EARTHING CONTACTS ASSOCIATED EACH WITH THE CORRESPONDING MAIN CONTACT, SAID EARTHING CONTACTS BEING MOUNTED COAXIALLY WITHIN AND IN ELECTRICAL CONTACT WITH THE CORRESPONDING MAIN CONTACT, SAID THIRD AND FOURTH EARTHING CONTACTS BEING SLIDABLY MOUNTED AND SO DIMENSIONED AS TO BE CAPABLE OF BEING EXTENDED TO ENGAGE RESPECTIVELY SAID FIRST AND SECOND EARTHING CONTACTS WHEN THE CIRCUIT-BREAKER ASSEMBLY IS IN ITS "ISOLATED POSITION, AND COMPRISING EARTHING MEANS INCLUDING AN EARTHED CONTACT SELECTIVELY TO EARTH SAID THIRD AND FOURTH MAIN CONTACTS, WHEREBY SAID FIRST AND SECOND MAIN CONTACTS MAY SELECTIVELY BE EARTHED THROUGH THE FIRST AND THIRD EARTHING CONTACTS AND THE SECOND AND FOURTH EARTHING CONTACTS RESPECTIVELY AND THROUGH SAID CIRCUIT-BREAKER MEANS. 